This invention relates to electronic type polyphase electric energy meters.
In general, in order to measure an electric power or energy of a polyphase n-wire system, it is necessary to provide n-1 wattmeters or electric power measuring devices according to Blondel's theorem. Therefore, out of the conventional polyphase power measurements, for instance in a three-phase 3-wire power measurement, the two-wattmeter method is employed or an electronic type electric power measuring device having a plurality of operation circuits is employed.
However, polyphase electric power or energy meters according to the conventional art are intricate in construction and operation. Especially, conventional electronic type electric energy meters employed in the conventional art are each composed of a number of component parts and are therefore undesirable with respect to reliability and economy. Furthermore, the characteristics of the measuring elements of the conventional polyphase electric energy meter are not uniform, which causes interphase unbalance errors. Since the interphase unbalance errors must be corrected, the conventional polyphase energy meters have been manufactured by complicated manufacturing processes, and therefore the measurement accuracy thereof is limited.